The findings indicate the U.S. Environmental Protection Agency, EPA, is greatly underestimating local and regional impacts of mercury emissions, but also show that mercury levels in fish and wildlife can decline when airborne mercury emissions from nearby sources are decreased.
Published in this month’s issue of 'BioScience,' the two new studies are part of a three year research effort coordinated by the Hubbard Brook Research Foundation, HBRF.
'There is still a lot that we don't understand about mercury, but it is clear that biological mercury hotspots occur and that mercury emissions from sources in the U.S., as opposed to China and other countries overseas, are the leading cause,' said Charles Driscoll, a Syracuse University environmental systems engineering professor and a principal investigator with Hubbard Brook.
The five hotspots identified by the 11 member research team include the west and central Adirondack Mountains in New York, the upper Connecticut River in New Hampshire and Vermont, the lower and middle Merrimack River in New Hampshire and Massachusetts, the upper Androscoggin and Kennebec rivers in Maine, and central Nova Scotia.
In addition, the researchers, who analyzed mercury levels in fish, birds and mammals, identified nine other suspected hotspots in New England and southeastern Canada.
Mercury from power plants and other sources is deposited in the environment, where it can be transformed into methyl mercury, a deadly neurotoxin that can cause reproductive harm to fish and wildlife, as well as neurological damage to humans. Concern about mercury contamination has prompted 44 states to issue fish consumption advisories for mercury.
Ecological conditions play a significant role in the creation of mercury hotspots, scientists explained Tuesday at a press briefing in Washington DC.
Some watersheds are more sensitive to mercury pollution because of ecological impacts from acid rain, such as the hotspots found in the Adirondack Mountains and in Nova Scotia. In addition, both areas have shallow soils that facilitate the transfer of mercury to surface waters and contain extensive wetlands that promote conversion to methyl mercury.
Reservoirs where water flows are raised and lowered for power production and other purposes also appear to be particularly vulnerable to becoming biological mercury hotspots, as evidenced by analysis of reservoirs in New Hampshire and Maine.
Water fluctuations in the reservoirs provide prime conditions for the bacteria that produce methyl mercury, the researchers said.
Analysis of mercury deposition patterns around the hotspot in southern New Hampshire and northeastern Massachusetts found that local emission sources - four coal-fired power plants - contribute 65 percent of the mercury deposited in the environment.
The researchers estimated the mercury deposition in this hotspot is 10 to 20 times higher than pre-industrial conditions and five times higher than EPA estimates.
'Our modeling results support a growing body of evidence that a significant fraction of the mercury emitted from coal-fired power plants in the U.S. is deposited in the area surrounding the plants,' said Thomas Holsen, a civil and environmental engineering professor at Clarkson University in New York and co-author of the studies.
The new research contradicts the Bush administration’s contention that mercury deposition and contamination is driven by global emissions of the toxic metal – a major reason cited by officials when they finalized the mercury emissions trading program in March 2005.
Set to take effect in 2010, the cap-and-trade plan aims to cut mercury emissions from power plants by some 70 percent by 2025.
The plan allows some plants to purchase credits instead of cutting emissions. Opponents contend this will create local hotspots of mercury pollution, but EPA officials have downplayed their concern. More than a dozen states have filed suit to block the regulations.
And at least 24 of 30 states that have formally responded to the rule have called for more stringent cuts and many have called for no mercury emissions trading within their borders, according to HBRF’s Kathy Fallon Lambert, a study coauthor.
'These studies validate state concerns about hotspots,' she told reporters. 'EPA is underestimating local deposition and projecting a future based on incomplete information.'
The findings of the studies grabbed the attention of Senator Susan Collins, a Maine Republican, who announced today that she will introduce legislation to cut mercury emissions by 90 percent and to create a nationwide network to monitor mercury contamination.
'I have long-argued that EPA used faulty science in order to justify an insufficient mercury rule, and these studies prove it,' Collins said.
EPA Deputy Press Secretary Jessica Emond defended the mercury rule, noting that it makes the United States 'the first nation in the world to regulate mercury emissions from coal-fired power plants.'
Emond added the agency is 'currently working to establish a coordinated, nationwide network of atmospheric mercury monitoring sites for estimating dry deposition.'